Preparation and potential of chitosan-based/Al2O3 green hydrogel composites for the removal of methyl red dye from simulated solution.

Different dyes are discharged into water streams, causing significant pollution to the entire ecosystem. The present work deals with the removal of acid red 2 dye (methyl red-as an anionic dye) by green sorbents based on chitosan derivatization. In this regard, two classes of chitosan derivatives-a total of six-were prepared by gamma irradiation at 30 kGy. The first group (group A) constitutes a crosslinked chitosan/polyacrylamide/aluminum oxide with different feed ratios, while the second group, identified as group B, is composed of crosslinked carboxymethyl chitosan/polyacrylamide/aluminum oxide with different ratios. Glycerol was added to soften the resultant hydrogels. The products were characterized by different tools, including FTIR for confirming the chemical modification, TGA for investigating their thermal properties, and XRD for verifying their crystalline structure. The morphology of the prepared derivatives was studied through SEM, while their topography before and after dye adsorption was monitored via the AFM. The removal efficiencies of the prepared sorbents were verified at different operation conditions, such as pH, temperature, adsorbent dose, initial concentration of dye solutions, and contact time. The data revealed that the optimum conditions for maximum dye uptake were as follows: pH 4, contact time 120 min, 0.1-g sorbent dose, and 50-ppm dye concentration. Additionally, the prepared sorbents demonstrated potent adsorption capacity and removal efficiency. It was found that the elements of the second group displayed higher performance than their counterparts. The data showed also that the adsorption process best fits with the Freundlich model and obeyed pseudo-first-order kinetic isotherm. In addition, the synthesized composites showed observable antibacterial potency toward E. coli as a Gram-negative bacterium and S. aureus as a Gram-positive bacterium.

Petroleum sludge formation and its treatment methodologies: a review.

Different petroleum operations produce huge amount of oil sludge annually. For instance, US EPA estimates the annual sludge production of each US refinery of 30,000 tons, while the average oily sludge produced from petrochemical industries in China is estimated about 3 million tons per year. In the last year, our center could recover about 30,206 barrels of raw oil from 32,786 barrels of tank bottom sludge (TBS) for different petroleum companies. This sludge causes huge economic losses besides its negative environmental impacts. The accumulation of sludge in the tanks results in reducing the tanks' capacity for storing liquid crude, accelerating the corrosion of the tanks, delay in the production schedule, and disturbing the whole production operation. There are diverse treatment methodologies such as solvent treatment, addition of certain chemicals, and centrifuging. Of course, the environmental regulations and the overall cost limitations are very important in deciding the preferred applicable method(s). Although several works handled the problem of sludge deposition and treatment from different aspects, we intend to introduce a different work. First, composition, formation, types, and properties of TBS were reviewed. Then, environmental and economic problems caused by TBS were revised. At last, different methodologies applied for treatment of oily TBS to recover oil and safe disposal of hazardous remains were investigated focusing on the most straightforward and environmentally friendly protocols. It is expected that this review attracts the experts in petroleum chemistry, and other relevant fields and provides a comprehensive understanding of current sludge control and treatment research.